Fouling deterrent chemical defence in three muricid gastropod egg masses from the Southeast coast of India

Abstract

The egg masses of the marine muricid gastropod molluscs Chicoreus virgineus, Chicoreus ramosus and Rapana rapiformis were studied for antifouling activities. The minimum inhibitory concentrations of crude extracts for the inhibition of byssal production and attachment of the brown mussel Perna indica were 650 μg ml⁻¹, 1150 μg ml⁻¹ and 925 μg ml⁻¹ from the three muricid gastropods, respectively. Higher LC₅₀ values than EC₅₀ values and 100% recovery of the mussels in the toxicity assay indicated the non-toxic nature of the extracts. The gradient partitioning of the egg mass extracts and subsequent antimicrofouling screening against 40 biofilm bacteria showed wide-spectrum antibacterial activity of the medium polar fraction from C. virgineus; the non-polar fraction from R. rapiformis and both non-polar and medium polar fractions from C. ramosus. The antimicrofouling activity from extracts of the three egg masses was found to be more prominent than antimacrofouling activity. This may be attributed to the targeting of a defence strategy against microbes in order to protect the developing mollusc embryos.

Keywords:

• Muricid
• egg masses
• antifouling
• mussel bioassay
• antibacterial assay
• Chicoreus ramosus
• Chicoreus virgineus
• Rapana rapiformis

Acknowledgements

The authors gratefully acknowledge the facilities provided by SDMRI and the first author is thankful to the Tropical Marine Mollusc Programme (TMMP)-DANIDA project for a fellowship to carry out the work.